Storing numbers from a file to an array

Question

I am coding an algorithm that takes a file from the command prompt and stock its numbers into an array.

The file looks like this:

12 563 898 521

And here is the code:

// INCLUSION
#include <stdio.h>
#include <stdlib.h>

//  CODE

void howto(const char *) ;

int main(int k, const char *argv[])
{   if (k < 2) howto(*argv) ;
    int i = 0, array[2500] ;
    FILE * R = fopen(argv[1], "r") ;

    // pass file content to array
    if (! R) return 1 ;
    while (!feof(R)) {
        fscanf(R, "%d ", &array[i]) ;
        i++ ; }
    fclose(R) ;
    for(int x = 0 ; x < i ; x++ ) {
        printf("lol : %d\n", array[x]) ; }
    return 0 ; }

void howto(const char *P) {printf("Expected: %s <file to read>\n", P) ; }

The code run without warnings but has no result: it sorts of run forever. I am guessing my issue comes to my while loop, but I have not been coding in C for a while and I have no idea why the syntax is not having the intended effect. Any ideas?

Thank you!

[Why is “while ( !feof (file) )” always wrong?](https://stackoverflow.com/questions/5431941/why-is-while-feof-file-always-wrong) — Eugene Sh., Apr 27 '18 at 13:57
Please use an orthodox C layout style, preferably Allman or 1TBS. Pico style is OK for Pico, but not for C. — Jonathan Leffler, Apr 27 '18 at 14:00
Note that a trailing blank in a `scanf()`-family format string is awful if the input will ever be interactive. Also, you should check that you don’t overflow the array. — Jonathan Leffler, Apr 27 '18 at 14:04
@JonathanLeffler can you elaborate on the reason why I shouldn't use a blank in my fscanf? — Joanny Rouviere, Apr 27 '18 at 14:20
@InTheMoodForNow You can start with the Wiki: https://en.wikipedia.org/wiki/Indentation_style#Styles — Christian Gibbons, Apr 27 '18 at 14:26
See [Trailing blanks in `scanf()` format strings](https://stackoverflow.com/questions/19499060/) for a good discussion. — Jonathan Leffler, Apr 27 '18 at 14:56

score 1 · Accepted Answer · edited Apr 27 '18 at 14:58

1

Read manual page of fscanf & Check the return value. man 3 fscanf says

These functions return the number of input items successfully matched and assigned, which can be fewer than provided for, or even zero in the event of an early matching failure

Replace

while (!feof(R)) {
      fscanf(R, "%d ", &array[i]) ;
      i++ ; 
}

with

while (i < 2500 && fscanf(R, "%d ", &array[i]) == 1) { /*return 1 if read one item */
      i++ ;
}

Also read Why is “while ( !feof (file) )” always wrong?

edited Apr 27 '18 at 14:58

Jonathan Leffler

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answered Apr 27 '18 at 14:01

Achal

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I was sure it came from that while! Thank you so much for the in-depth answer to read too. Solved my issue and told me why I had it in the first place ;). – Joanny Rouviere Apr 27 '18 at 14:17

Storing numbers from a file to an array

1 Answers1